A touch panel is a type of user interface device that may be attached to a surface of a display device or a projection surface. Traditional touch panels, although widely used, is unable to detect multiple fingers or objects on a surface. If two or more fingers are simultaneously touched, the touch panel may stop working or it may report only one of the touch positions or an inaccurate phantom touch position.
The interface of controlling a machine using multiple fingers has a long history even before the computer was invented (e.g. piano, control panel, DJ mixer, etc). As computers become available to more populations and become increasing powerful, the human computer interface has evolved more and more natural to the users representing real interactions in our physical world. In the early days, computers used punched cards as input. Later, console and keyboard interface was introduced. However, at that time, computer users were still limited to programmers and trained staffs because users had to remember all the command and parameters in order to interact with computers. The use of WIMP (Window, Icon, Menu, Pointing device) greatly simplified the task. Virtual buttons including icons, menus represent physical operations in a 2D graphical way so that a pointing device (e.g. mouse, touch screen) can simulate clicks on it intuitively. However, unlike interactions in our real world, WIMP is limited to single point inputting device (e.g. the user can use mouse to point to only a single location at one time). This limitation results in serious inefficiency. One logical operation may require a series of mouse clicks and mouse moves. For example, a user may click on multiple levels of menus and move across the screen to access buttons, icons in order to perform one logical operation. Imagine if we have only one finger instead of ten in our everyday life, the life would be very difficult for us. In addition, WIMP is limited to single user, multi-user operation is not possible because only one mouse/pointing device is available system wide. The use of multi-pointing device (e.g. a touch screen that can detect locations of multiple fingers simultaneously) can significantly increase interaction efficiency and allows multi-user collaborations.
A traditional infrared touch panel comprises an array of light transmitters on two adjacent sides of the touch panel and an array of light detectors on the other two adjacent sides of the touch panel. Each light transmitter corresponds to one light detector on the opposite position. The transmitter and detector layout formed X and Y light beam paths, where a single finger touch on the surface will block one X light beam and one Y light beam. The touch coordinates and size of the touch area can then be determined by the intersection of the blocked X beam and Y beam. The problem associated with light beam matrix touch screen is that it cannot accurately detect multiple touch positions simultaneously. For example, if there are two fingers touching the surface at the same time, four light beam intersection points will be found. Two of the intersection points will be phantom points. The actual touch positions cannot be determined on such light beam matrix touch panel.
In short, the input vector generated by a traditional touch panel is a singleton <P1>, where P1 is the location of a touch point. It is therefore an object of the present invention to provide more dimensions and features of the touch property to allow sensible control and a new generation of interaction.
Singleton touch input vector generated by a traditional infrared touch panel:
<P1>
Multi-dimensional touch input vector generated by the present invention:
<  <touch_id_1, P1, size1, convex_contour1>,  <touch_id_2, P2, size2, convex_contour2>,  <touch_id_3, P3, size3, convex_contour3>,  ...>